Optical component, optical device and optical communications system

Abstract

The present invention relates to an optical component and the like having a structure that can increase the absolute value of the angular dispersion, and also can reduce the temperature dependence of the diffraction angle. The optical component comprises a diffraction grating element of a transmissive type and a prism. The prism is composed of a material with a refractive index of n 1 , and the diffraction grating element and the prism are surrounded a material with a refractive index of n 0 .

1. An optical component comprising:
 a diffraction grating element of transmissive type having a flat plate, and a diffraction grating formed on one surface of said flat plate or formed within said flat plate in parallel with the one surface thereof; and 
 a prism composed of a material with a refractive index of n 1 , said prism having a first surface on which the light diffracted by said diffraction grating element is incident, and a second surface from which the light having passed through the first surface is emitted; 
 wherein said diffraction grating element and said prism are provided within a medium with a refractive index of n 0 ; and 
 wherein, in the case that light with a wavelength λ is incident on said diffraction grating element at an incident angle of θ 0 , then taking the incident angle of the light incident on the first surface of said prism, from said diffraction grating element, to be θ 2 , taking the emission angle of the light emitted from said second surface of said prism to be θ 5 , taking the temperature coefficient of the diffraction angle in said diffraction grating element to be F g , taking the temperature coefficient of the emission angle θ 5  of the light emitted from the second surface of said prism, assuming that the incident angle θ 2  of the light incident on the first surface of said prism is fixed regardless of the temperature, to be F p , and taking the magnification rate of the angular dispersion caused by said prism to be M p , said diffraction grating element and said prism are arranged such that the wavelength λ and the incident angle θ 0  satisfy the following relationship: 
 “n 1 >n 0  AND |θ 5 |>|θ 2 |” or 
 “n 1 <n 0  AND |θ 5 |<|θ 2 |”, 
 whilst also satisfy the following relationship: 
 “−2M p F g <F p <0” or 
 “−2M p F g >F p >0”. 
 
   
   
     2. An optical component according to  claim 1 , wherein said diffraction grating element and said prism are mutually separated by a predetermined distance, by means of said medium with the refractive index of n 0 . 
   
   
     3. An optical component according to  claim 1 , wherein said diffraction grating element is attached to the first surface of said prism by means of an adhesive. 
   
   
     4. An optical component according to  claim 1 , wherein, in a temperature range of −20° C. to +80° C., said optical component satisfies the following relationship:
 “F p =−M p F g ”. 
 
   
   
     5. An optical component according to  claim 1 , wherein, taking the temperature coefficient of the emission angle θ 5  of the light emitted from the second surface of said prism to be F t , and taking the angular dispersion of the emission angle θ 5  to be D t , the absolute value of the ratio (F t /D t ) is less than 0.4 pm/° C. in a temperature range of −20° C. to +80° C. 
   
   
     6. An optical component according to  claim 5 , wherein, in a temperature range of −20° C. to +80° C., the absolute value of the ratio (F t /D t ) is less than 0.2 pm/° C. 
   
   
     7. An optical component according to  claim 1 , wherein, taking the angular dispersion of said diffraction grating element to be D g , taking the temperature coefficient of the angular dispersion D g  to be G g , and taking the temperature coefficient of the magnification rate M p  of the angular dispersion caused by said prism to be H t , then said optical component satisfies the following relationship:
 “−2M p G g <H t D g <0” or 
 “−2M p G g >H t D g <0”. 
 
   
   
     8. An optical component according to  claim 7 , wherein, in a temperature range of −20° C. to +80° C., said optical component satisfies the following relationship:
 “−M p G g =H t D g ”. 
 
   
   
     9. An optical component according to  claim 1 , wherein, taking the grating period of said diffraction grating to be Λ, then the temperature coefficient of the product (n 0  Λ) has a negative value, and the temperature coefficient of the ratio (n 1 /n 0 ) has a negative value. 
   
   
     10. An optical component according to  claim 1 , wherein said prism is composed of a semiconductor. 
   
   
     11. An optical component according to  claim 10 , wherein said semiconductor is silicon. 
   
   
     12. An optical device including an optical component according to  claim 1 , wherein said optical device multiplexes or demultiplexes light by using said optical component. 
   
   
     13. An optical device according to  claim 12 , further comprising a housing hermetically sealing said optical component therein. 
   
   
     14. An optical communications system including an optical device according to  claim 12 , wherein said optical communications system transmits signal light, and multiplexes or demultiplexes it by using said optical device.